Non-contact tool setting device and method

Abstract

To provide a method and a device for evaluating a tool profile.SOLUTION: A receiver generates a beam intensity signal that describes an intensity of received light. A non-contact tool setting device is attached to a coordinate positioning device such as a machine tool that enables movement of a tool 80 with respect to the non-contact tool setting device. A method includes using the coordinate positioning device for moving the tool 80 with respect to the non-contact tool setting device along a tool inspection path 88. The tool inspection path is selected so that a light beam advances substantially along a circumference of a peripheral edge of the tool 80 to be inspected. When the tool inspection path 88 is passed, beam intensity data, which describes the beam intensity signal generated by the receiver, is collected, and analysis of the collected beam intensity data is used for evaluating a tool profile.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a non-contact tool setting device for a coordinate positioning device, and more particularly to an improved method and apparatus for measuring the profile of a tool.

Background Art

[0002] A beam interruption tool setting device for use in a machine tool is known, for example, from Patent Document 1. This type of tool setting device includes a light source that generates a light beam that is advanced to a photodetector. During a tool setting operation, the machine tool is operated to move a tool into and out of the light beam. The interruption of the light beam by the tool is detected by analyzing the detector output signal, and the device generates a so-called "trigger signal" to indicate to the associated machine tool that the light beam has been interrupted. Typically, this trigger signal is issued when the light level reaches 50% of the "beam passing" state (i.e., when 50% of the light beam is prevented from reaching the detector). The machine tool records the position of the tool relative to the tool setting device upon receipt of the "trigger signal", thereby enabling a single position on the tool edge to be determined. This measurement operation can be repeated a plurality of times in order to measure a plurality of different positions one by one on the edge of the tool. Thus, this arrangement enables the tool size, such as the length and / or diameter of the tool, to be measured.

[0003] Patent Document 2 describes an alternative method for generating a “trigger signal” during measurement movements in which a rotating or non-rotating tool is brought in and out of a light beam. In particular, Patent Document 2 describes digitizing the detector output signal and identifying minimum and / or maximum values ​​of the digitized data corresponding to one or more teeth of the cutting tool entering and exiting the beam during the measurement movement. The digital processor determines in real time whether the minimum / maximum values ​​fit a curve of a desired type and issues a trigger signal only if such a fitting curve exceeds a threshold. In this way, it is possible to measure the position of a single point on the tool during their entry and exit from the light beam. For stationary tools, the measured position is on the edge blocking the light beam. For rotating tools with multiple cutting teeth that are rotated in and out of the beam, the measured position is on the cutting edge having the largest diameter. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] U.S. Patent No. 6,496,273 [Patent Document 2] European Patent Application Publication No. 1587648 [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, the tool setting device described above allows the position of a point on the edge of the tool to be established relatively quickly, and thus enables the provision of measurements of the tool length or diameter. It is also possible to measure the tool profile by repeating the measurement movement to measure multiple different points along the edge of the tool, but such a process can be very time-consuming (i.e., the tool must be moved in and out of the beam multiple times) and is generally considered impractical. Further details of such prior art tool measurement processes are described below with reference to Figure 9a. [Means for solving the problem]

[0006] According to a first aspect of the present invention, a method is provided for evaluating the profile of a tool using a non-contact tool setting device comprising a transmitter that emits a light beam and a receiver that receives the light beam, wherein the receiver generates a beam intensity signal representing the intensity of the received light, and the non-contact tool setting device is mounted on a coordinate positioning device that allows the tool to be moved relative to the non-contact tool setting device, and the method is as follows: (i) A step of using a coordinate positioning device to move a tool relative to a non-contact tool setting device along a tool inspection path, wherein the tool inspection path is selected such that a light beam travels substantially along the periphery of the tool being inspected. (ii) A step of collecting beam intensity data that describes the beam intensity signal generated by the receiver when the tool inspection path of step (i) is passed, and (iii) The process includes analyzing the beam intensity data collected in step (ii) to evaluate the tool profile.

[0007] Accordingly, a first aspect of the present invention relates to a method for evaluating the profile of a tool using a non-contact tool setting device. The profile to be evaluated is the shape, position, or dimensions of one or more cutting structures of the tool. The non-contact tool setting device includes a beam-blocking type tool detection system in which a beam of light (e.g., a laser beam) emitted from a transmitter (e.g., by a laser diode of the transmitter) is passed through a region of free space to a receiver. The receiver detects the received light (e.g., using a photodiode) and generates a beam intensity signal representing the intensity of the received light. The non-contact tool setting device is mounted on a coordinate positioning device such as a machine tool, which can be programmed to move the tool relative to the non-contact tool setting device. Relative movement can be given by moving the tool and / or the non-contact tool setting device.

[0008] The method of the present invention includes step (i) using a coordinate positioning device to impart relative motion between a light beam and a tool and define a tool inspection path. In particular, step (i) includes moving the tool relative to a non-contact tool setting device such that the light beam travels along the periphery of the tool. Thus, the coordinate positioning device is positioned to move the light beam along a tool inspection path, resulting in the light beam being scanned along the periphery of the tool. In other words, the tool inspection path is selected such that the light beam is moved in a direction substantially tangent to the periphery of the tool. This should be contrasted with the prior art described above, in which the tool is moved so that it enters and exits the light beam (i.e., in a direction substantially perpendicular to the edge of the tool) in order to acquire a measurement point.

[0009] For a stationary tool, the periphery of the tool is simply the edge of the tool to be inspected. If the tool is rotating, the tool inspection path is set to advance the light beam along the outermost range of the multiple edges of the rotating tool. Thus, the movement of the light beam along the periphery of the tool is performed in addition to any rotational tool movement (e.g., rotation of the tool around its longitudinal axis) which results in various parts of the tool's periphery being rotated in and out of the light beam. The movement of the light beam along the periphery of the tool is preferably linear (translational) motion only and does not involve any rotational motion. In other words, the tool inspection path preferably defines only the linear motion of the tool relative to the light beam (e.g., motion along the mutually orthogonal x, y, and / or z axes). Depending on the shape of the tool, the tool inspection path may be linear and / or may include one or more curved sections to follow the periphery of a curved tool. The tool inspection path may pass through only a portion of the tool to be measured, or it may pass around the entire periphery of the tool. Preferably, at least a portion of the light beam strikes the tool while it passes through the tool inspection path. As described below, the tool inspection path may include a single path around the edge of the tool, or it may include multiple paths around the edge of the tool.

[0010] Step (ii) includes sampling the beam intensity signal generated as the tool inspection path passes, thereby generating beam intensity data. For example, the beam intensity signal may be digitized by an analog-to-digital converter to generate a set of beam intensity data. In other words, the beam intensity signal, which represents the level of beam occlusion, will typically change as the tool inspection path passes. Step (ii) includes periodically sampling the beam intensity signal to generate beam intensity data to be analyzed. Any appropriate sampling rate may be used. For example, a higher sampling rate may be used for a rotating tool (e.g., to obtain beam intensity data that describes beam occlusion as the tool is rotated). The sampling rate may be changed as the optical beam passes through the tool inspection path, allowing more beam intensity data to be collected in a particular area of ​​the tool. It should also be noted that the optical beam may pass through the tool inspection path at a single constant speed, and may be moved at different speeds as it passes along different parts of the tool inspection path. Furthermore, there may be one or more dwell periods defined as part of the tool inspection path during which the light beam is not moved relative to the tool (however, the tool itself may continue to rotate during such dwell periods). Beam intensity data collected during such dwell periods is particularly useful when measuring rotating tools (for example, to enable the measurement of the positions of multiple points around the tool, such as the edges of different cutting teeth). During such dwell periods, it is also possible to obtain more accurate information from the coordinate positioning device regarding the tool position relative to the non-contact tool setting device.

[0011] As described below, the collected beam intensity data contains information about the tool profile. Therefore, step (iii) includes analyzing the beam intensity data using one of the techniques described below. The analysis may include analyzing all of the collected beam intensity data, or it may include selecting a subset of the data (e.g., from a region of interest along the tool inspection path or from multiple regions). In this way, the tool profile can be evaluated.

[0012] Therefore, the present invention provides a quick and simple technique for measuring the profile of a tool. Instead of individually measuring multiple points around the tool by repeatedly driving the tool in and out of the light beam, as in the touch-trigger type measurement described above, the periphery of the tool can be measured in detail by a scanning type operation that advances the light beam around the periphery of the tool. This makes the tool profiling process quick and easy.

[0013] Advantageously, the tool inspection path is selected so that the light beam travels along a path aligned with nominal positions around the tool. In other words, the tool inspection path can be generated using knowledge of the nominal or expected tool profile. For example, the tool inspection path can be generated from tool design (e.g., CAD) data of the tool. For a tool that conforms to its nominal specifications, the tool inspection path can be selected so that, as the tool passes through the tool inspection path, the light beam is blocked at a specific preset level (e.g., 50%). Thus, a deviation in beam intensity data from the preset level indicates that the tool profile deviates from the nominal value. Therefore, process (iii) may include evaluating whether the collected beam intensity data corresponds to the data expected if the profile of the tool being inspected conforms to its nominal profile. A deviation exceeding a certain amount can be used to indicate that the required tool tolerance is not met. Alternatively, the deviation can be used to adjust the assumed dimensions of the tool.

[0014] As described above, any deviation in beam intensity data from a preset level (e.g., from the 50% level) can be used to indicate that the tool profile deviates from the nominal value. Furthermore, a calibration process may be performed before measurement to identify any changes in the beam intensity signal that would occur when a specific displacement exists at the position of the tool edge in the optical beam. For example, a calibration table or function describing the relationship between the tool edge position in the beam and the beam intensity signal may be generated. It should be noted that the relationship between the tool edge position and the beam intensity signal can be nonlinear, especially with respect to larger changes in position within the beam. Such a calibration process may include, for example, moving the tool edge from a position resulting in 50% beam occlusion at small intervals (e.g., 10 μm intervals) and recording the resulting beam intensity signal at each position. This type of calibration allows any change in the beam intensity signal (e.g., a shift from 50% to 60% or 50% to 40%) to be converted into a displacement or shift of the tool edge position. In this way, the assumed dimensions of the tool can be adjusted based on the acquired measurements.

[0015] Advantageously, step (iii) includes comparing the beam intensity data collected in step (ii) with previously acquired beam intensity data. The comparison may be a direct comparison of individual beam intensity data values, or an indirect comparison (e.g., of the minimum intensity values ​​for the rotary tool as described below) may be performed. Conveniently, the previously acquired beam intensity data may include data collected from previous measurements of the same tool. For example, the previously acquired beam intensity data may be collected before the tool is used for cutting purposes, or the previously acquired beam intensity data may include data collected from measurements of a reference tool having the same nominal profile as the tool. In other words, a “golden” or reference tool nominally identical to the tool being measured may provide a reference or baseline measurement on which the beam intensity data collected in step (ii) is compared. Thus, step (iii) may conveniently provide an indication of whether the tool profile has changed relative to previous measurements. This may include indicating whether any significant portion of the tool profile has changed by an amount that could impair cutting performance. Thus, the indication may include setting an error flag when a particular change in the tool profile occurs.

[0016] The method may be performed using a non-rotating tool (i.e., the only movement during measurement may be the movement of the tool relative to the light beam along the tool inspection path). Alternatively, the tool may be rotated during measurement. Thus, the tool may be held on a rotatable spindle of a coordinate positioning device. The tool may include one or more cutting teeth located around its radius. Conveniently, the tool may be rotated around its longitudinal axis while being moved along the tool inspection path. In this way, during the rotation of the tool, different cutting teeth enter and exit the light beam in sequence, generating minimum and / or maximum values ​​in the beam intensity data. Thus, step (iii) may conveniently include identifying minimum and / or maximum values ​​in the beam intensity data. Identification of such minimum and / or maximum values ​​may be performed by a digital signal processing method of the type described in Patent Document 2.

[0017] Advantageously, the tool includes multiple cutting teeth. Conveniently, step (iii) includes identifying the minimum and / or maximum values ​​associated with each tooth of the tool. In this way, it is possible to evaluate the profile of each tooth individually. For example, variations in the minimum and / or maximum values ​​associated with a tooth that occur as the tool inspection path is passed can be used to evaluate the profile of that tooth. This makes it possible to perform individual profiling of different teeth of a rotary tool in a single pass of the tool inspection path. For example, the size deviation of an individual tooth can be determined using previously acquired calibration data as described above, or any such deviation can be compared to previous measurements. In addition to identifying the minimum and / or maximum values, the shape of the minimum and / or maximum values ​​can be used to infer specific tool profile information. Thus, step (iii) may include analyzing the shape of the minimum and / or maximum values ​​in order to evaluate the profile of the tooth that produces the minimum and / or maximum values.

[0018] Advantageously, step (ii) includes digitizing the beam intensity signal to generate beam intensity data. This is done using an analog-to-digital converter (ADC) to sample the beam intensity signal. A sampling rate of at least 10 kHz is preferably used (for example, for a tool rotating at 3000 rpm). Conveniently, a sampling rate of at least 100 kHz is used. Sampling frequencies of 100 kHz to 500 kHz may be conveniently used. Advantageously, step (iii) includes analyzing the beam intensity data using a digital signal processor (DSP). This may be performed after all data has been collected, or the analysis may be started while data is still being collected. As described above, a constant sampling rate may be used. Alternatively, the sampling rate may be changed as the tool inspection path is passed.

[0019] The tool inspection path can be pre-calculated before the coordinate positioning device moves the tool. In other words, the tool inspection path may include a pre-programmed path that the coordinate positioning device is programmed to follow before process (i) begins. Instead of such known path techniques, the tool inspection path may be generated during process (i) using feedback passed from a non-contact tool setting device to the coordinate positioning device. For example, the tool inspection path may be selected to maintain the beam intensity signal within a specific range.

[0020] Any suitable coordinate positioning device can be used to carry out this method. Advantageously, the coordinate positioning device is a machine tool (e.g., a computer numerically controlled or CNC machine tool). Alternatively, the coordinate positioning device may be a coordinate measuring machine (CMM), a flexible gauge (such as the Equator system sold by Renishaw plc in Wotton-Under-Edge, UK), or an offline tool inspection device.

[0021] The non-contact tool setting device used in the method may include separate transmitter and receiver units, each of which may be mounted on a bracket. Alternatively, a single unit including the transmitter and receiver may be provided. The device may include an interface separate from the transmitter / receiver unit, or the interface may be formed integrally with such unit. A processor may be provided to perform step (iii) of the method. An ADC may be provided to perform step (ii). The processor and / or ADC may be located in a separate processing unit within the interface, or provided as part of a coordinate positioning device.

[0022] Advantageously, the transmitter includes a laser for generating light. The transmitter may also include an optical system for providing a collimated light beam. Alternatively, the transmitter may provide a focused laser beam (rather than being collimated). The light beam may have a substantially elliptical or circular profile (e.g., a Gaussian beam profile). The light beam may have a diameter of less than 0.5 mm, less than 1 mm, less than 2 mm, or less than 3 mm.

[0023] A second aspect of the present invention includes an apparatus for performing non-contact tool profile measurement on a coordinate positioning apparatus, the apparatus including a transmitter that emits a light beam, a receiver that receives the light beam and generates a beam intensity signal that describes the intensity of the light received by the receiver, an analog-to-digital converter that generates beam intensity data from the beam intensity signal, and a processor for analyzing the beam intensity data, the processor being configured to evaluate the profile of the tool by analyzing the beam intensity data generated when the tool is moved along a tool inspection path, the tool inspection path being selected to advance the light beam around the periphery of the tool. The apparatus may include any one or more of the above features in the context of a similar method.

[0024] According to a third aspect of the present invention, there is provided a method of measuring a tool using a non-contact tool setting device including a transmitter that emits a light beam and a receiver that receives the light beam, the receiver generating a beam intensity signal that describes the intensity of the received light, the non-contact tool setting device being attached to a coordinate positioning device that enables the tool to be moved relative to the non-contact tool setting device, the method comprising: (i) using the coordinate positioning device to move the tool through the light beam, and (ii) during step (i), collecting beam intensity data that describes the beam intensity signal generated by the receiver, and (iii) comparing the beam intensity data collected in step (ii) with previously acquired beam intensity data, the comparison providing an indication of whether the profile of the tool has changed. Step (i) may include moving the tool along a tool inspection path, and the previously acquired beam intensity data may have been created by moving the tool along the same inspection path.

[0025] The present invention will then be described by way of example only, with reference to the accompanying drawings.

Brief Description of the Drawings

[0026] [Figure 1] A diagram showing the non-contact tool setting device of the present invention. [Figure 2] A diagram showing a cutting tool along the periphery of which a light beam is moved. [Figure 3] A diagram showing beam intensity data collected when passing through the path shown in FIG. 2. [Figure 4] A diagram showing a multi-tooth cutting tool that is rotated while being moved along an inspection path along its periphery. [Figure 5] A diagram showing beam intensity data collected when passing through the path shown in FIG. 4. [Figure 6] A diagram showing the minimum values of the intensities associated with different teeth of the tool shown in FIG. 5, plotted as a function of the position along the inspection path. [Figure 7] This figure shows the minimum intensity curve plotted against previous measurements of the same tool. [Figure 8] This diagram shows how a camera is used to photograph any specific tool defect. [Figure 9a] This diagram shows a conventional tool inspection process. [Figure 9b] This figure shows the tool peripheral scanning method of the present invention. [Figure 9c] This figure shows the tool peripheral scanning method of the present invention. [Modes for carrying out the invention]

[0027] Referring to Figure 1, a tool setting device of the present invention is shown. The device includes a transmitter 10 for generating a substantially collimated light beam 12. The transmitter 10 includes a laser diode and appropriate optics (not shown) for generating the collimated light beam 12. A receiver 14 for receiving the light beam 12 is also shown. The receiver includes a photodiode (not shown) for detecting the light beam 12.

[0028] Both the transmitter 10 and the receiver 14 are fixed to a common base 20 by support columns 18. This arrangement ensures that the transmitter 10 and the receiver 14 maintain a constant distance and orientation from each other. The base 20 can then be mounted directly to the bed of the machine tool, or in fact, to any suitable part. It should also be noted that various alternative structures can be used for mounting the transmitter and receiver. For example, a common housing may be provided for the transmitter and receiver, or separate transmitter and receiver units may be mounted separately to the machine tool.

[0029] The apparatus also includes an interface 15 connected to the transmitter 10 and receiver 14 via an electrical cable 17. The interface 15 provides power to the transmitter 10 and receiver 14 and also receives beam intensity signals from the photodiode detector of the receiver 14. The interface 15 includes an analog-to-digital converter (ADC) 18 that samples the analog beam intensity signal generated by the receiver 14 and generates a stream of digital beam intensity values. This stream of digital beam intensity values, also called beam intensity data, is passed to a digital signal processor (DSP) 20 for analysis. The results of the analysis may be passed to the machine tool 30 via a link 28. In this example, the ADC 18 and DSP 20 are located in the interface 15, but they could be included in any part of the system (e.g., the receiver, the machine tool control unit, etc.). Up to this point, the apparatus is similar to that described in Patent Document 2.

[0030] Next, with reference to Figures 2 and 3, the tool profile evaluation technique of the present invention will be described for non-rotating tools. Figure 2 shows a cutting tool 50 including a cutting edge 52. The cutting tool has a nominal tool profile and is held by a movable spindle (not shown) of a machine tool. The position of the cutting tool and the position of the tool setting device within the machine tool are known, and the machine tool can be programmed to move the cutting tool 50 relative to the tool setting device.

[0031] During use, the machine tool is configured to move the tool, and the light beam first strikes a first point 54 on the periphery of the tool. At this initial position, approximately 50% of the light beam is obscured. Next, the tool is moved, and the light beam travels along the tool inspection path around the periphery of the tool (as shown by a pair of dashed lines 56) until it reaches a second point 58. It can be understood that the movement along the tool inspection path is substantially tangential to the periphery of the tool. During the movement of the beam along the tool inspection path 56, beam intensity data, generated by the ADC 18 of the tool setting device from the beam intensity signal, is collected and stored.

[0032] Referring to Figure 3, the beam intensity data 60 is plotted as a function of position P along the tool inspection path. If the machine tool moves the tool at a constant speed, the relative position along the tool inspection path can be easily estimated from the time the beam intensity data is acquired. Figure 3 also shows the nominal or predicted beam intensity data 62 that would be predicted if a tool of nominal dimensions were moved along the same tool inspection path. The difference between the collected beam intensity data 60 and the predicted beam intensity data 62 provides a measure of how much the tool 50 deviates from its nominal size and shape.

[0033] Referring next to Figure 4, a rotatable cutting tool 80 having four cutting teeth is shown. It should be noted that three teeth 82a, 82b and 82c are shown by solid lines, while the fourth tooth 82d, located on the rear surface of the tool shaft in the orientation shown in Figure 4, is shown by a dashed line. The tool 80 is measured while it is rotated around its longitudinal axis R by the spindle of the machine tool in which it is held. The light beam travels around the periphery of the tool along the tool inspection path. In particular, the tool inspection path extends around the periphery of the tool from a first point 84 to a second point 86. The spatial extent of the light beam as it passes through the path is shown by a dashed line 88. During the movement of the beam along the tool inspection path, beam intensity data generated by the ADC18 of the tool setting device is collected and stored.

[0034] Figure 5 shows a portion of the beam intensity data collected during tool inspection, as described with reference to Figure 4. The beam intensity data is plotted as a function of position P along the tool inspection path. Again, this position can be inferred from the time of data acquisition if the path is traversed at a constant speed. The tool is continuously rotating during measurement, and therefore the beam intensity data includes minimums that occur when each of the four cutting teeth significantly obstructs the beam. A series of minimums are generated sequentially by each of the four teeth as they rotate in the beam. Thus, the minimums labeled a, b, c, and d in Figure 5 correspond to beam shielding obtained when each of the four different cutting teeth 82a-d obstructs the beam, respectively. The minimums can be identified by the DSP20 using any of the techniques described in Patent Document 2. Furthermore, the DSP20 can be configured to separate the minimums obtained from different teeth of the cutting tool.

[0035] Figure 6 shows the beam intensity at each identified minimum, plotted as a function of position along the tool inspection path. In particular, curves 90a, 90b, 90c, and 90d show the minimums resulting from teeth 82a, 82b, 82c, and 82d, respectively. It should be noted that only a small amount of collected beam intensity data (i.e., data collected during three rotations of the tool) is shown in Figure 5, and the curves in Figure 6 are generated from a large number of such minimums. Thus, curves 90a, 90b, 90c, and 90d show the degree to which each of the four different teeth 82a, 82b, 82c, and 82d of the cutting tool obscures the light beam as the tool inspection path is passed by the rotating tool.

[0036] The data plotted in Figure 6 allows for the identification of chipping or material accumulation on any tooth of the cutting tool. In particular, the peaks 92 of curve 90d indicate chipping on tooth 82d of the tool, resulting from an increase in the minimum intensity associated with tooth 82d as the chip allows more light to pass through to the receiver. Similarly, the valleys 94 of curve 90c indicate excess material accumulation on tooth 82c, resulting from a further decrease in the minimum intensity associated with tooth 82c as the excess material blocks more light. Furthermore, the location of defects (e.g., chipping or excess material) on each tooth can be determined from the locations P of the peaks and / or valleys along the tool inspection path.

[0037] The minimum value shown in Figure 6 allows for the determination of the presence and location of defects. Furthermore, as shown in Figure 7, it is also possible to compare a plot of minimum values ​​measured for a given tool with previously acquired minimum data for that tool. In particular, the process of determining the intensity of a given identified minimum value as a function of its position along the tool inspection path can be repeated multiple times. For example, such minimum value data can be collected from the tool before it is used for cutting purposes. Thus, a reference curve 100 can be obtained that provides information about the profile of an unused tool. After the tool has been used in a cutting operation, the measurement process can be repeated using the same tool inspection path. A minimum value curve 102 is then generated and can be compared with the reference curve 100. Any differences between wear, chipping, or material deposition on the cut surface, as indicated by the curves, can be identified from the difference between curve 102 and the reference curve 100. The plot difference (i.e., subtracting curve 102 from curve 100, or vice versa) can be used to provide a visual representation of any existing differences.

[0038] Referring to Figure 8, the addition of a camera for visually inspecting the tool is illustrated. In particular, Figure 8 shows a tool setting device 150 of the type described above, which emits a light beam 152 and is mounted on the bed 160 of the machine tool. The tool setting device 150 is positioned to inspect the tool 170 held by the spindle 172 of the machine tool when its tool is positioned in the region 174 of the light beam 152. As described above, the tool setting device 150 makes it possible for defects 188 in the tool 170 to be identified, and in particular, it makes it possible to determine the location of such defects on the tool. In addition to the tool setting device 150, a front-illuminated camera system 180 may also be provided. The camera system emits a white light beam 182 and can capture an image of any object located within its field of view 184. The positions of the field of view 184 are known to the tool setting device 150, i.e., they are separated by a position difference V.

[0039] During use, the tool setting device 150 is used to identify defects 188 on the tool 170. The position of the tool setting device 150, the camera's field of view 184, and the tool 170 are all known in the machine tool's coordinate system. This means that as the machine tool moves the spindle 172, the defects 188 on the tool 170 identified by the tool setting device 150 may be positioned within the camera system 180's field of view 184. This allows for the capture of an image of the tool defect and further allows the operator to assess the nature of the detected defect. The tool setting device 150 is preferably of the type described above, but may include any tool setting device.

[0040] For completeness, a detailed comparison of the present invention with conventional tool setting techniques will be shown with reference to Figures 9a-9c.

[0041] Referring to Figure 9a, a prior art tool measurement process is shown. As described in the introduction above, the light beam of the prior art non-contact tool setting device is moved toward the tool 202 from an initial position 204 away from the tool 202. In practice, the light beam is usually stationary, and the tool is moved within the light beam, but the same relative motion occurs as if the light beam were being moved. Thus, the light beam moves along a path substantially perpendicular to the edge of the tool 202 being measured. In Figure 9a, the light beam is initially at the starting position 204. At point 206, where the tool 202 covers 50% of the light beam, a trigger signal is emitted by the non-contact tool setting device. The machine tool receives the trigger signal and records the location where the trigger event occurred. This allows the position of a single point 208 on the surface of the tool 202 to be determined. This process can be repeated to measure multiple points on the tool edge.

[0042] Figure 9b illustrates the tool measurement process according to the present invention. As described above, the light beam is directed to a starting position 222 on the edge of the tool. In this example, a tool of nominal dimensions would cover approximately 50% of the light beam. The light beam then travels along the periphery of the tool from the starting position 222 to the ending position 224 (the path followed by the light beam is the so-called tool inspection path). Beam intensity data is collected at several points 226 along the tool inspection path. The tool inspection path may travel in continuous motion (e.g., at a constant speed) or its speed may be varied as the path is traversed. It is also possible to remain at each of the points 226 (i.e., momentarily stop the movement of the light beam relative to the tool), and optionally, an averaging procedure can be performed at each point (e.g., to improve the signal-to-noise ratio of the beam intensity data and / or to obtain a more accurate measurement of the tool's position relative to a non-contact tool setting device).

[0043] For a perfect tool (i.e., a tool that precisely corresponds to the nominal tool profile), (in this example) 50% of the light beam will be obscured at each point along the tool inspection path. For an actual tool (a tool that has worn or experienced material deposition during machining), any local deviation at the tool's edge position will result in the amount of light beam obscured differing from the 50% level expected for the nominal tool. In other words, the deviation of the beam intensity data from the expected 50 percent at each point 226 indicates that the tool is either greater than expected (obscuring more of the light beam) or smaller than expected (obscuring less of the light beam). The beam intensity data is combined with information from the machine tool describing the position of the light beam 220 at each point 226 to provide multiple measurements of the tool's surface position. In this way, multiple points 226 can be measured in a high-speed scanning motion without the need to move the tool back and forth in the beam, as in the prior art method shown in Figure 9a.

[0044] Referring to Figure 9c, it should be noted that the tool inspection path may include multiple passes along the periphery of the tool. This may be done, for example, when the uncertainty of the nominal position of the tool edge is significantly greater than the width of the light beam.

[0045] Figure 9c shows a tool inspection path in which the light beam is moved linearly downward from an initial position 250 to a first position 252. The light beam is then advanced laterally to a second position 254 before being moved linearly upward to a third position 256. It is then advanced laterally to a fourth position 258 before being moved linearly downward to a final position 260. The linear movement between the second position 254 and the third position 256 is sufficient on its own to measure the edge of tool 264 at its nominal position, but it would not be able to measure a tool displaced by more than the beam width from its nominal position (for example, to the tool position indicated by the dashed contour of tool 266). However, providing multiple paths would allow for the measurement of larger displacements of any such position (or tool size). For example, the beam intensity data collected when the light beam moves from the fourth position 258 to the final position 260 would allow for the measurement of the edge of tool 266 with a dashed contour. Of course, if, for example, the tool is bent and different regions of the tool edge are in different passes of the light beam, it is also possible to use beam intensity data from different passes of the light beam. As an alternative to such multi-pass techniques, the width of the light beam can be increased.

[0046] Those skilled in the art will understand that modifications to the above embodiments are possible. For example, the method can be carried out using a non-contact tool setting device attached not only to a machine tool but also to any coordinate positioning device (e.g., a CMM, robot, offline tool inspection system, etc.).

Claims

1. A non-contact tool setting device comprising a transmitter that emits a light beam and a receiver that receives the light beam, wherein the receiver generates a beam intensity signal describing the intensity of the received light, and the non-contact tool setting device is mounted on a coordinate positioning device that allows the tool to be moved relative to the non-contact tool setting device, and a method for evaluating the profile of a tool using the non-contact tool setting device, the method being: (i) A step of using the coordinate positioning device to move the tool relative to the non-contact tool setting device along a tool inspection path, wherein the tool inspection path is selected such that the light beam travels substantially along the periphery of the tool being inspected, (ii) A step of collecting beam intensity data that describes the beam intensity signal generated by the receiver when the tool inspection path passes through in step (i), (iii) A step of performing machining using the coordinate positioning device and the tool, (iv) A step of using the coordinate positioning device to move the tool relative to the non-contact tool setting device along the same tool inspection path used in step (i), (v) A step of collecting beam intensity data that describes the beam intensity signal generated by the receiver when the tool inspection path passes through in step (iv), A method comprising: (vi) comparing the beam intensity data collected in step (ii) with the beam intensity data collected in step (v) by direct comparison of individual beam intensity data values, and determining from there any change in the profile of the tool brought about by the machining in step (iii), wherein the beam intensity data collected in step (ii) is data obtained from the tool before it was used to perform the machining in step (iii).

2. A method according to claim 1, characterized in that the tool is held on a rotatable spindle of the coordinate positioning device, the tool is rotated about its longitudinal axis, while the tool is moved along the tool inspection path of steps (i) and (iv).

3. A method according to claim 1 or 2, characterized in that the tool inspection path includes a pre-programmed path which is programmed to be followed by the coordinate positioning device before the commencement of process (i).

4. A method according to any one of claims 1 to 3, characterized in that the sampling rate used to collect the beam intensity data in step (ii) is the same as the sampling rate used to collect the beam intensity data in step (v).

5. A method according to any one of claims 1 to 4, wherein steps (ii) and (v) include collecting the beam intensity data, while the tool moves relative to the non-contact tool setting device.

6. A method according to any one of claims 1 to 5, characterized in that there is no feedback from the non-contact tool setting device to the coordinate positioning device while the tool is moving along the tool inspection path in steps (i) and (iv).

7. A method according to any one of claims 1 to 6, wherein step (vi) includes using a deviation in the profile of the periphery of the tool to calculate one or more prepared dimensions of the tool, and the method further includes a step (vii) of using the coordinate positioning device and the tool to perform further machining using the one or more prepared dimensions.

8. A method according to any one of claims 1 to 7, wherein the tool comprises a plurality of cutting teeth and rotates during steps (i) and (iv).

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